Drive and control system for diagnostic and therapeutic exercise treadmill

ABSTRACT

An improved drive and control system for an exercise treadmill is provided which incorporates safety features for the prevention of a start-up at high belt speed after the treadmill has been turned off, or upon the resumption of power after a power failure, and to prevent rapid acceleration of the belt to a high speed condition in the case of certain control circuit failures. Circuitry, or other means, has been included in the drive system as an interlock whereby the manual on-off switch which activates the drive motor will not be effective until the motor speed control has been reset to the zero speed position. In addition, circuitry is included to provide for shutting down the drive motor in the event of a failure or malfunction in its control circuitry which could cause an unscheduled rapid increase in the treadmill belt speed to a high speed condition.

United States Patent n91 Cherry [54] DRIVE AND CONTROL SYSTEM FORDIAGNOSTIC AND THERAPEUTIC EXERCISE TREADMILL [75] Inventor: Raymond I.

Calif.

Cherry, Torrance,

[73] Assignee: Del Mar Engineering Laboratories, Los Angeles, Calif.

[22] Filed: Nov. 29, 1971 [2]] Appl. No.: 202,754

[52] US. Cl ..338/200, 272/69, 200/50 C [51 Int. Cl. ..A63b 23/06 [58]Field of Search ..338/200, 201, 198, I72, I73;

272/69; 200/42 R, 172 R, [72 A, 50 C;

[ Jan. 16, 1973 Primary Examiner-Bernard A. Gilheany AssistantExaminerD. A. Tone Attorney-Keith D. Beecher [57] ABSTRACT An improveddrive and control system for an exercise treadmill is provided whichincorporates safety features for the prevention of a start-up at highbelt speed after the treadmill has been turned off, or upon theresumption of power after a power failure, and to prevent rapidacceleration of the belt to a high speed condition in the case ofcertain control circuit failures. Circuitry, or other means, has beenincluded in the drive system as an interlock whereby the manual onoffswitch which activates the drive motor will not be effective until themotor speed control has been reset to the zero speed position. lnaddition, circuitry is included to provide for shutting down the drivemotor in the event of a failure or malfunction in its control circuitrywhich could cause an unscheduled rapid increase in the treadmill beltspeed to a high speed condition.

7 Claims, 6 Drawing Figures PATENTED JAN 16 I973 SHEET 1 BF 2 408.5400Owwmm I NVENTOR. RAY/40410 I. Cmszey DRIVE AND CONTROL SYSTEM FORDIAGNOSTIC AND THERAPEUTIC EXERCISE TREADMILL BACKGROUND OF THEINVENTION The drive and control system of the present invention may beused, for example, in conjunction with the diagnostic and therapeuticexercise treadmill described and claimed in copending application, Ser.No. 103,155, which was filed Dec. 31, 1970, in the name of Joseph A.Hesen, and which is assigned to the present assignee. However, it willbecome evident as the present description proceeds, that the drive andcontrol system of the invention has general utility in conjunction witha wide variety of exercise treadmills, and the like.

As described in the aforesaid copending application, it is the usualprior art practice for electrocardiograms to be taken of patients in aresting position on a table or bed. However, it has been found that aresting patient may often produce a normal electrocardiogram, eventhough there is clinical or other evidence of abnormalities. It has beenfound, for example, that more conclusive electrocardiograms may beobtained if the patient is subjected to a continuous exerciserepresenting a constant work load which may be graded at various timeintervals. The treadmill has proven to be a suitable instrument forthat, and other purposes, and clinical treadmill stress testing hasbecome widespread as a basis for the study and diagnosis of the physicalcondition of patients.

An important objective of the present invention is to provide anappropriate drive and control system which renders the electric motorpower driven treadmill absolutely safe, and easy to operate. Forexample, it is known to the art to provide a manual speed control inconjunction with the power driven treadmill, whereby the attendingphysician, or the patient himself, may control the treadmill belt speedfrom a low to a relatively high value.

It is usual in the prior art power driven treadmills to drive thetreadmill belt with an alternating current electric motor, and to varythe speed of the motor over a limited range by varying the appliedvoltage. Some treadmills have been provided in the art with mechanicalvariable speed control mechanisms, and some with hydraulic drives.However, with such equipment, it is difficult to obtain a smooth controlto zero speed while operating under load. An improved drive for thetreadmill belt which permits a smooth speed control to zero speed isobtained by using a high-permeability permanent magnet direct-currentmotor, and by varying the direct-current voltage applied to the motor byan appropriate speed controller. Such a motor provides the necessaryhigh torque at low speeds, and is capable of providing, for example,smoothly variable belt speeds in a range from -10 miles an hour.

A suitable speed controller for use in conjunction with such adirect-current motor incorporates, for example, a bridge rectifierincluding silicon controlled rectifiers, or the like, which arecontrolled so that a varying amplitude direct-current voltage may beapplied to the direct-current motor for speed control. However, there isa possibility for the silicon controlled rectifiers, or other elementsin such a controller to burn out or malfunction, and this can result inthe controller introducing maximum direct-current voltage to the motorwhich, in turn, results in an unanticipated abrupt rise in the motorspeed from the controlled level to a maximum level.

Such an unscheduled increase in the motor speed can be hazardous, andgives rise to the possibility of injury to the patient using thetreadmill. The control system to be described incorporates appropriatecircuitry which responds to an unanticipated rise in the direct-currentvoltage applied to the motor which could result, for example, from theaforesaid malfunction in the control circuit, and which serves tode-energize the motor and shut down the system in the presence of such acondition.

The control system to be described also includes interlocking meanswhich may be of a mechanical or electrical nature, and which preventsthe drive motor from being activated until the speed control has beenset to a zero or reset position. Such an interlocking means prevents theactivation of the drive motor by the main switch when the speed controlis in any position other than zero. Without this feature, it would bepossible for a patient to be standing on the belt, with the speedcontrol setting at some value other than zero, and with the resultingunanticipated and rapid acceleration of the belt up to the set speed,with possible injury to the patient, when the switch is turned on.

A further feature of the electrical interlocking circuit to be describedis that in the event of a power failure, or should the power cable forthe treadmill be unplugged from the power main receptacle, while thetreadmill is operating; the drive motor will not be energized when poweris restored, unless the speed control is first reset to zero. Thislatter control prevents possible injury to a patient who is standing onthe belt when power is restored, since it prevents the belt from rapidlyaccelerating to the preset speed, and requires a resetting of the systembefore it again becomes operational.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective representationof treadmill apparatus which may be constructed to incorporate theimproved drive and control system of the invention;

FIG. 2 is a front view of a control unit for the treadmill of FIG. 1,illustrating certain indicators and controls for the treadmill;

FIG. 3 is an enlarged fragmentary perspective view of a mechanicalinterlock between a power switch and speed control which are included inthe unit of FIG. 2;

FIG. 4 is a sectional view of a latch component of the interlock of FIG.3, taken essentially along the line 4- 4 of FIG. 3;

FIG. 5 is a circuit diagram of an equivalent electrical interlockbetween the power switch and speed control of the unit of FIG. 2; and

FIG. 6 is a' circuit diagram of an overspeed protection circuit for thedrive motor of the treadmill of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS The treadmill shownin FIG. 1 includes an endless belt 10 riding on rollers 11 and 13 which,in turn, are mounted on appropriate bearings attached to a frame 15. Thebelt 10 is driven, for example, by means of a motor 12 through anappropriate drive such as a toothed belt 14. Power in the form of llO-volt AC current from the usual mains is supplied through a connector16 to an electric control module 18 which, in turn, is controlled by aspeed control rheostat 22 in a control unit 20, to control the speed ofthe motor 12. The control unit 20, as described in the aforesaidcopending application, may be mounted on a handle section 21 of thetreadmill, for appropriate control by the patient himself, or it may beremoved for remote control by the attending physician, or otherattendant. When activated, the motor 12 drives the belt in the directionof the arrow, and at a speed set by the setting of the speed control 22.

As shown in FIG. 2, the speed control rheostat 22 in the control unitincludes a knob which is turned, for

example, in a clockwise direction to increase the motor speed, and whichis turned in a counterclockwise direction to reduce motor speed. Thespeed control 22 may be turned in the counterclockwise direction to azero reset position, at which the motor speed is zero. A snap-actingtoggle-type manual on-off master power switch 24 is positioned on thecontrol unit 20 adjacent to the speed control 22, as shown in FIG. 2. Aspeed control indicator 25 is also mounted on the control unit, and itmay be directly calibrated in miles per hour (mph).

As stated above, an important objective of the present invention is toprevent any activation of the drive motor 12 when the on-off switch 24is turned on, unless the speed control 22 has been turned back to itszero reset position, at which the speed of the belt 10 is reduced tozero. As will be described, this objective may be achieved in accordancewith the invention, either mechanically, as shown in FIGS. 3 and 4, orelectrically as shown in FIG. 5.

The mechanical assembly of FIG. 3 comprises a pinion 26 which engages arack 30 on a slide 32, the slide being held in position by bearingsurfaces in bulkheads 34 and 36, such that its left-hand end will enterthe area 42 in the switch button of the power switch 24 when the slideis moved to the left in FIG. 3. The pinion is attached to the shaft 28of the speed control 22, so that rotation of the speed control 22results in correspondingrotation of the pinion. In order to cause theleft-hand end of the slide 32 to be removed completely from the area 42of the switch button 40, so as to permit full freedom in the movement ofthe master switch 24 from one position to the other, the speed control22 must be turned in the counterclockwise direction to its zero or resetposition, at which position the shaft 28 turns the pinion 26 to anangular position so as to displace the slide 32 to the right in FIG.3,'thereby removing the left-hand end of the slide from the aforesaidarea 42.

With the master switch 24 in the off" position, illustrated in FIG. 3,rotation of the speed control 22 and pinion 26 in the clockwisedirection from the reset position to increase the speed of the belt 10,drives the left-hand end of the slide into the area 42 and over aspring-loaded latching cam 44. The latching cam 44 is a part of thelatch assembly shown in FIG. 4. As illustrated in FIG. 4, the latchingcam 44 is contained in the body of the switch button 40, and in itsnonnal position is caused to protrude by the force of a spring 48. The

master switch is now prevented from being switched to its on" positionby the presence of the latch cam 44, so long as the left-hand end of theslide 32 is in the area 42. However, when the speed control is returnedto the zero reset position, the left-hand endof the slide 32 is removedfrom the area 42, and the switch 24 may then be turned on by depressingthe switch button 40 so as to pivot the button in a counterclockwisedirection about the axis A in FIG. 3.

Should the speed control be turned while the switch 24 is in its onposition, the end of the slide 32 enters the area 38 under the latchingcam 44. Now, when the switch button 40 is pivoted in a clockwisedirection about the axis A to its of position, the end of the slide 32moves up the inclined surface 46 of the latching cam 44, and forces thecam into the cavity in the switch button 40 against the force of thespring 48. The left-hand end of the slide 32 then moves into the area42, and the latching cam 44 snaps out to its outer position, therebytrapping the slide 32, and preventing the switch 24 to be returned toits on state, until the speed control 22 has been returned to zero,thereby removing the left-hand end of the slide 32 from the area 42.

The interlock between the power switch 24-and the speed control 22 canbe achieved electrically, as shown by the circuit of FIG. 5. The circuitof FIG. 5 includes a normally open solenoid-operated relay switch 50which includes a relay coil 54 connected in series with the incomingalternating-current power line. The relay switch 50 is connected, forexample, to the control module 18 which supplies the direct-currentpower to the motor 12. In its normal state, the relay switch 50 preventsthe How of alternating current to the control module 18, so that thedrive motor 12 which, in turn, drives the treadmill belt 10, isdeenergized. The coil 54 of the relay switch 50, which when energizedcloses the relay switch, is included in the circuit in series with aswitch 56 The switch 56 is an integral part of the speed control 22, andis closed only when the speed control is returned to its reset position.i

As shown in FIG. 5, the master switch 24 is a twopole switch. One of thepoles of the switch 24 completes the circuit to the relay coil 54, onlywhen the switch 56 is closed, so that the relay 54 can be energized onlywhen the speed control 22 is in its reset position. The other pole ofthe switch 24 serves as a holding circuit to maintain the relay coil 54energized after the speed control is subsequently turned from its resetposition and the switch 56 is open. However, when the power switch 24 isactuated to its off position, the circuit cannot be energized until thespeed control 22 has again been turned to the reset position to closethe switch 56. Also, if power is lost for any reason, such as a powerfailure, or the power cable becoming unplugged, the speed control 22must be turned back to reset" before the motor 12 can again beactivated.

It is clear, therefore, that the speed control 22 must be returned toits reset" position before any belt speed can be resumed. In this way,the belt 10 of the treadmill can be started only after the speed control22 has been turned back to the zero speed condition of the belt.

As mentioned above, the circuit of FIG. 6 shows the drive system for themotor 12, and it includes a safety circuit for preventing overspeed ofthe belt of the treadmill due to a failure in the control circuit of themotor 12.

In the circuit of FIG. 6, the control module 18 includes a rectifierpower supply 19 which is energized from the alternating-current powersource when the relay switch S0 is closed. The rectifier 19 develops thedirect-current voltage for the motor 12, and the amplitude of thisvoltage is controlled so as to control the speed of the motor. Forexample, the rectifier power supply 19 may include a usual bridgerectifier which incorporates silicon controlled rectifiers in two of itsarms. The direct-current voltage supplied to the motor 12 from therectifier power supply 19 may be in the form of unfiltered, partialhalf-waves which, in turn, are controlled by the setting of the speedcontrol 22 which, in turn, controls the silicon controlled rectifiers inthe bridge network. Such variable controlled rectifier power suppliesare known. However, should a silicon controlled rectifier, or otherelement in the power supply malfunction, an unscheduled and abrupt riseto maximum direct-current output could result, and this could result inan unexpected rapid acceleration of the motor 12 from its set speed to amaximum speed, with possible injury to the person using the treadmill.For that reason, a safety circuit designated 62 is incorporated into thecontrol module, which will now be described.

The direct-current output from the rectifier 19 is connected to apotentiometer R4A which is included in the speed control 22, and whichhas a movable element connected to the base of a PNP transistor Q1. Thecollector of the transistor O1 is connected to the negative outputterminal of the power supply 19, and the emitter is connected to thecathode of a diode CR1. The anode of the diode CR1 is connected throughthe coil of a relay K1, through a further diode CR2, and through aresistor R3 to one terminal of the motor 12. The positive terminal ofthe power supply 19 is directly connected to the other terminal of themotor 12. The speed control 22 includes a further potentiometer R413which moves in unison with the potentiometer R4A, and which is connectedby way of terminals P1, P2 and P3 to the rectifier power supply 19. Thepotentiometer R4A serves to control the timing of the firing of theaforesaid silicon controlled rectifiers, and thereby controls theeffective amplitude of the direct-current voltage applied to the motor12, in a manner known to the art.

A resistor R1 and capacitor C1 are connected from the junction of thediode CR1 and relay coil K1 to the positive terminal of the power supply19, and a resistor R2 and capacitor C2 are connected from the junctionof the diode CR2 and resistor R3 to the aforesaid positive terminal. Therelay K1 has a normally closed contact in circuit with the energizingcoil 54 of the power switch 50.

The setting of the potentiometer R4A provides a reference voltage at thebase of a PNP transistor Q1. The transistor 01 is connected as anemitter follower, the emitter of which being connected through a diodeCR1 to a resistor R1. The collector of the transistor Q1 is connected tothe negative terminal of the power supply 64, whereas the resistor R1 isconnected to the positive terminal. The resistor R1 is shunted by acapacitor C1. The diode CR1, resistor R1 and capacitor C1 are allconnected to the other side of the energizing coil of the relay Kl.

The setting of the potentiometer R4A provides a reference voltage at thebase of the emitter follower transistor Q1, and this results in anegative reference voltage across the resistor R1 in the emitter circuitof the transistor. This voltage is stored in the capacitor C1 for aperiod of time sufficientto permit the voltage lag of the motor 12 toequalize any change in the field current, when the potentiometer R4Bsection of the speed control is changed rapidly for a reduced beltspeed. This storage across the capacitor C1 is necessary to preventoperation of the relay K1, with a resulting full shutdown of the system,when the speed control 22 is rapidly turned in the reduce speeddirection. The voltage stored by the capacitor C1 provides a referencevoltage for the relay Kl.

The relay K1 is a conventional l2-volt relay, for example, whichtypically operates when 6 volts is placed across the coil or across itsenergizing coil, or when the current in its energizing coil in eitherdirection exceeds a minimum value. The relay K1, therefore, acts as adif ferential switch, and opens the circuit of the energizing coil 54 ofthe relay switch 50 to shut down the system whenever the voltagedifferential across the capacitor C1 and resistor R2 exceeds apredetermined level. When the relay coil 54 is energized, the motor 12cannot again be energized until the speed control 22 is returned to thereset position to close the switch 56.

Therefore, if, for any reason, the voltage introduced to the motor 12 bythe control module 18, and which appears across the terminals B1 and B2,exceeds by a predetennined amount the reference voltage established bythe setting of the speed control 22, the relay K1 is activated to shutdown the system, thereby preventing an unexpected acceleration of themotor 12. Since the shut down operation is desired only where the motorvoltage materially exceeds the reference voltage, the diode CR2 isincluded in the circuit to prohibit any excitation of the relay Klexcept when the motor voltage exceeds the reference voltage, and notvice versa. In this way, inadvertent shut down of the system isobviated, for any condition except when the motor voltage 12 rises abovethe reference voltage so as to indicate the existence of a runawaycondition.

The drive circuit of FIG. 6 causes the treadmill to continue to operatesatisfactorily so long as the motor and reference voltages are inbalance. However, the safety circuit 62 in the drive circuit constantlycompares the reference voltage and the motor voltage, so that anyfailure, for example, in the control module 18, whereby the directcurrent output voltage to the motor 12 increases beyond a predeterminedamount, causes a flow of current in the differential relay K1. This, inturn, causes the relay K1 to be activated to open the circuit of theenergizing coil 54 of the relay switch 50. As mentioned above, with thecoil 54 deenergized, the relay switch 50 reverts to its normally openposition thereby interrupting the flow of alternating current to thecontrol unit 18, and effectively arresting the motion of the treadmillbelt 10. The response to such an unbalance beyond a predetermined amountbetween the reference voltage and the motor voltage is almostinstantaneous and the shut down of the treadmill is accomplished withoutthe patient sensing any particular increase in belt speed.

The invention provides, therefore, an improved drive and control systemfor an exercise treadmill, and one which incorporates safety features,so that the use of the treadmill, and especially for therapeuticpurposes, is safe and foolproof.

While particular embodiments of the invention have been shown anddescribed, modifications may be made. It is intended in the followingclaims to cover all modifications which fall within the spirit and scopeof the invention.

What is claimed is:

1. In an exercise treadmill having an endless belt and an electric drivemotor for the belt, a drive and control system for said motor including:an input circuit adapted to be connected to a source of electricalenergy; a control circuit connected to said input circuit and responsiveto electrical energy from said source for introducing control energy tosaid drive motor; a manually adjustable speed control for controllingthe speed of said motor; an electric switch for controlling theactivation of said motor; and interlocking means intercoupling saidspeed control and said electric switch to prevent said motor from beingactivated until said speed control is adjusted to a particular position.

2. The combination defined in claim 1, in which said speed controlcomprises potentiometer means included in said control circuit, and saidelectric switch is interconnected between said input circuit and saidcontrol circuit, said interlocking means preventing said control circuitfrom being energized until said potentiometer means is adjusted to aparticular position corresponding to zero speed of the motor.

3. The combination defined in claim 2, in which said electric switchincludes a manually movable button member having a slot therein, andwhich includes a slide member mechanically coupled to said potentiometermeans and movable into said slot to prevent actuation of said switchwhen said potentiometer means is turned away from a positioncorresponding to zero speed of said motor.

4. The combination defined in claim 3, and which includes aspring-loaded latch mounted on said button member to cause said buttonmember to latch with said slide member when said switch is actuated toits off position during a time when said potentiometer means is turnedaway from its aforesaid zero speed position.

5. The combination defined in claim 2, and which includes a relay switchin circuit with said input circuit to disconnect said input circuit fromsaid source of electrical energy; and a second switch in circuit withsaid relay switch and mechanically coupled to said potentiometer'meansto cause said relay switch to disconnect said inputcircuit from saidsource of electrical energy whenever said potentiometer means is movedfrom a position representing zero speed of said motor.

6. The combination defined in claim 1, and which includes circuitryconnected to said control circuit for disconnecting said input circuitfrom said source of electrical energy whenever the electrical controlenergy introduced to said drive motor by said control circuit exceeds aparticular reference level.

7. The combination defined in claim 6, in which said circuitry includesvariable potentiometer means included in said speed control, a source ofreference potential connected to said variable potentiometer means toestablish different reference potential levels for different settings ofsaid potentiometer means, a differential relay circuit connected to saidsource of reference potential, and a second circuit for introducing asecond potential to said differential relay representing the potentialintroduced to said motor for any particular setting of saidpotentiometer means, said relay responding to a predetermineddifferential between said reference potential and said second potentialto disconnect said input circuit from said source of electrical energy.

1. In an exercise treadmill having an endless belt and an electric drivemotor for the belt, a drive and control system for said motor including:an input circuit adapted to be connected to a source of electricalenergy; a control circuit connected to said input circuit and responsiveto electrical energy from said source for introducing control energy tosaid drive motor; a manually adjustable speed control for controllingthe speed of said motor; an electric switch for controlling theactivation of said motor; and interlocking means intercoupling saidspeed control and said electric switch to prevent said motor from beingactivated until said speed control is adjusted to a particular position.2. The combination defined in claim 1, in which said speed controlcomprises potentiometer means included in said control circuit, and saidelectric switch is interconnected between said input circuit and saidcontrol circuit, said interlocking means preventing said control circuitfrom being energized until said potentiometer means is adjusted to aparticular position corresponding to zero speed of the motor.
 3. Thecombination defined in claim 2, in which said electric switch includes amanually movable button member having a slot therein, and which includesa slide member mechanically coupled to said potentiometer means andmovable into said slot to prevent actuation of said switch when saidpotentiometer means is turned away from a position corresponding to zerospeed of said motor.
 4. The combination defined in claim 3, and whichincludes a spring-loaded latch mounted on said button member to causesaid button member to latch with said slide member when said switCh isactuated to its ''''off'''' position during a time when saidpotentiometer means is turned away from its aforesaid zero speedposition.
 5. The combination defined in claim 2, and which includes arelay switch in circuit with said input circuit to disconnect said inputcircuit from said source of electrical energy; and a second switch incircuit with said relay switch and mechanically coupled to saidpotentiometer means to cause said relay switch to disconnect said inputcircuit from said source of electrical energy whenever saidpotentiometer means is moved from a position representing zero speed ofsaid motor.
 6. The combination defined in claim 1, and which includescircuitry connected to said control circuit for disconnecting said inputcircuit from said source of electrical energy whenever the electricalcontrol energy introduced to said drive motor by said control circuitexceeds a particular reference level.
 7. The combination defined inclaim 6, in which said circuitry includes variable potentiometer meansincluded in said speed control, a source of reference potentialconnected to said variable potentiometer means to establish differentreference potential levels for different settings of said potentiometermeans, a differential relay circuit connected to said source ofreference potential, and a second circuit for introducing a secondpotential to said differential relay representing the potentialintroduced to said motor for any particular setting of saidpotentiometer means, said relay responding to a predetermineddifferential between said reference potential and said second potentialto disconnect said input circuit from said source of electrical energy.